Ignition distributor advance mechanism



Nov. 6, 1962 E. R. LARGES ETAL IGNITION DISTRIBUTOR ADVANCE MECHANISM 2 Sheets-Sheet 1 Filed Aug. 31, 1959 am am 06H m T P Mme v T H 2K.

TTSQ m wem i w Nov. 6, 1962 E. R. LARGES ET AL 3,062,929

IGNITION DISTRIBUTOR ADVANCE MECHANISM Filed Aug. 31, 1959 2 Sheets-Sheet 2 468I0|2 I6 20 24 28 32 36 40 f/VGl/VE SPEED fv/P. PM. x10 f PUZVENTORS 5 Qxvlssr 4/8655, E7- POBEPrK/ TPA/V/(ci EPED 61/6521? \QOIIQAQIIMM ATTORNEY United States Patent 9 3,962,929 IGNITIGN DISTRBBUTUR ADVANCE MECHANISM Ernest R. Larges, Southfield Township, Oakland County, Robert K. Frank, Mount Clemens, and Fred S. Kerr, Royal Oak, Mich, assignors to Holley Carburetor Company, Van Dyke, Mich, a corporation of Michigan Filed Aug. 31, 1959, Ser. No. 837,273 11 Claims. (Cl. zen-31 This invention relates generally to ignition distributors, and more specifically to those distributors which are responsive to variations in engine speed and load.

Many designs of distributors have been proposed and tried wherein vacuum forces are used to-regulate the timing advance and/or retard of the distributor. However, all of these designs have lacked the ability to maintain a fixed maximum ignition advance during eriods of Wideopen-throttle engine operation and still be capable of advances greater than that maximum during part throttle engine operation.

Accordingly, it is an object of this invention to provide means whereby an ignition distributor will have a fixed maximum ignition advance during periods of Wide-openthrottle engine operation and greater ignition advances during part throttle engine operation.

Other objects and advantages of the invention will become apparent when reference is made to the following specification and illustrations, wherein:

FIGURE 1 is a cross-sectional view of an ignition distributor constructed in accordance with the teachings of this invention, taken on line 1-1 of FIGURE 2 and looking in the direction of the arrows.

FIGURE 2 is a plan view partially in cross-section of the distributor of FIGURE 1, with the cap of FIGURE I removed.

FIGURE 3 is a graph illustrating the performance of a conventional distributor as compared to a distirbutor constructed in accordance with the teachings of this invention.

Referring now in greater detail to the drawings, FIG- URE 1 illustrates an ignition distributor 1% which may be comprised generally of a cup-shaped housing 12 including a depending reduced portion 14 having an opening 16 therethrough for the reception of a driving shaft 18. Bushingdike bearing members 26 and 22 may be provided in order to reduce the degree of friction between the rotating shaft 18 and surface of opening 16.

A breaker plate 24 mounted on a bearing member 26 is adapted to rotate about shaft 18 in a manner to be subsequently explained. The breaker plate 24 carries thereon a breaker arm assembly 27 which includes a cam engaging portion 28 engageable by the rotating cam 30 to effect make and break of the circuit at the contacts indicated at 32 (see FIGURE 2 also). The cam 30 is fixedly secured to the shaft 18 and is adapted to be rotated therewith. The shaft 18 can, of course, be rotated in timed relation with the engine by means of gear member 34 cooperating with some output transmission 36 of the engine.

An insulated rotor 38, having a spring-like electrical contact 4%) thereon, is secured to the upper portion of shaft 18 and is adapted to be rotated thereby in accordance with engine speed. Contact 40, which is continually biased against the ignition coil input terminal 42 of the distributor cap 44, is adapted to sequentially traverse the output terminals 46 of cap 414 and is in relative juxtaposition to one of said terminals whenever the electrical discharge occurs.

FIGURE 2, a plan view of the distributor with the cap 44 and rotor 38 removed, illustrates generally the adice Vance mechanism and its functional connection to the engine, the intake manifold of which is illustrated at 4%. The advance mechanism is controlled generally by the pressure responsive device 50 which communicates by means of suitable conduitry schematically illustrated at 52 with a port 54 in the carburetor 56. The carburetor S6 is located on the engine intake manifold 48 in such a manner so as to deliver a combustible mixture, the flow of which is controlled by the throttle valve 58, to the individual intake ports of the cylinders located in engine 60. Port 54 may be considered as a source of a combination of manifold vacuum and venturi vacuum as sensed by ports 62 and 64, respectively. Various valving arrangements not shown because they are not important to the invention may, of course, be associated with ports 62 and 64- in order to effect the proper combination of manifold and venturi vacuum, as is well known in the art.

The pressure responsive device 54 may be substantially comprised of a housing 66 and cover member 68 rigidly held together in a manner so as to peripherally secure a diaphragm member 70 therebetween. A member 72 connected at its one end to the diaphragm member '70, is adapted to be operatively engaged with breaker plate 24 as by means of hole formed therein for the reception of the end '74 of member 72. Any suitable retaining means such as a cotter pin 76 may be employed so as to prevent accidental disengagement between member 72 and breaker plate 24. Chamber 7% formed generally by cover 68 and diaphragm 7t) is exposed to a source of vacuum, as communicated by conduit 52, while the chamber 8% is vented to the atmosphere.

A movable abutment 82 is slideably received by cover 68 and is urged to the right by a spring 34, the preload of which can be varied by the adjustable spring seat 86. A housing portion 88 suitably secured to the cover 68 serves to both retain the seat 36 and communicate the vacuum to chamber 78 by means of passages 90 and 92 formed in abutment 82.

The entire pressure responsive device 50 can, of course, be secured to the housing 12 by any suitable means such as screws 94.

Calibrating springs 96 and 98 are secured at one end to the anchor pins 10% and 162 which in turn are fixedly secured to the housing 12. The other ends of springs 96 and 98 are connected to the braker plate spring posts 104 and 106. Openings 1% and 110 may, of course, be formed in the breaker plate 24 in order to provide the necessary clearance for anchor pins 106 and 102.

Operation URE 2.

Springs 96 and 93, being anchored at one end to the housing 12 by means of anchor pins and 162, respectively, and connected at their respective other ends to the breaker plate spring posts 104 and 106, urge the breaker plate 24 clockwise about shaft 18 until the holes 108 and 110 formed in the plate 24 abut against the anchor pins 100 and 192. This causes the breaker arm assembly 27 to be rotated to a position whereby the cam 30 will contact the cam engaging portion 28 at a time when the respective pistons within the engine are most nearly at top dead center.

When the throttle is moved to wide open position, the air flow by means of the venturi vacuum port 64 and the manifold vacuum by means of port 62 are sensed and communicated to chamber 78 generally by means of passages 52, 9t and 92. As the resulting vacuum increases, the diaphragm 7a is caused to move in ever increasing amounts to the left thereby rotating the breaker plate 24 and the breaker arm assembly 27 counter-clockwise about shaft 18 and cam 34). This causes the cam 36 to engage the cam en aging portion 23 at ever increasing degrees of engine crankshaft rotation ahead of when the engine pistons reach top dead center. This is usually referred to by those skilled in the art as degrees of ignition advance.

The invention as disclosed in FIGURE 2 continues this advance until the diaphragm comes into contact with the abutment 82 at which time the maximum wide-openthrottle advance will be realized. This is illustrated by the wide-open-throttle advance curve as determined by points A, F, C and D of FIGURE 3. The wide open curve may be considered as being common to both a conventional distributor and one constructed in accordance with this invention.

Past experience in the art and of engine design as shown that it is desirable to have such a maximum ignition advance during wide-open-throttle engine operation. Furthermore, it has also been known that better engine performance is achieved if ignition advances greater than that maximum are obtained during part throttle engine operation. However, the prior designs of distributors were incapable of achieving this additional advance since once the diaphragm as illustrated at 70 came in contact with its abt ment, further movement was impossible. This is illustrated by the part throttle curve determined by points A, B, C and D of FlGURE 3.

In contrast to prior designs, the invention not only provides means for obtaining a maximum ignition advance during wide-open-throttle engine operation as described above, but further provides means for obtaining a part throttle advance curve as determined by points A, B, E and D of FIGURE 3.

For example, if the engine were operating under wideopen-throttle conditions and the advance was at point E, any ubsequent throttle closing movement to reduce engine speed would result in a higher manifold vacuum than before. This higher vacuum would still be communicated to chamber '78 in a manner causing the diaphragm 70 to urge the abutment member 32 to the left against the resilient biasing force of spring 84. The particular spring rate of spring 84 and the geometry of the advance mechanism in general then determines the curves E, B, A for the respective vacuum values existing during all subsequent part throttle conditions. The po'nt E at which curve A, B, E intersects curve A, F, C, D is, of course, dependent on the amount of preload placed on spring 84 by the adjustable spring seat 86 which may be threadably received by housing portion 88.

The foregoing specification constitutes such a clear and concise disclosure as to enable anyone skilled in the art to practice the invention.

Other modifications of the invention are, of course, possible within the scope of the appended claims.

What we claim as our invention is:

1. An internal combustion engine ignition distributor of the type in which spark advance is dependent upon engine operating vacuum, said distributor comprising a housing, a shaft rotatably mounted through one end of said housing, a switch assembly, a cam member normally rotatable with said shaft and adapted to intermittently open and close said switch assembly for effecting a make and break of the ignition circuit, a breaker plate normally supporting said switch assembly and being adapted to have relative angular motion with respect to said housing, pressure responsive means operatively connected to said housing for rotating said breaker plate in accordance with vacuum applied thereto, and abutment means positioned in the path of travel of said pressure responsive means, said abutment means being adapted to positively stop further angular motion of-said breaker plate at a d. predetermined vacuum and to allow further angular motion of said breaker plate at vacuums a predetermined amount greater than said predetermined vacuum.

2. An internal combustion engine ignition distributor of the type in which spark advance is dependent upon engine operating vacuum, said distributor comprising a housing, a shaft ro-tatably mounted through one end of said housing, a switch assembly, a cam member normally rotatable with said shaft and adapted to intermittently open and close said switch assembly for effecting a make and break of the ignition circuit, means for rotating said switch member relative to said housing, pressure responsive means operatively connected to said housing for rotating said switch assembly in accordance with vacuum, and abutment means positioned in the path of travel of said pressure responsive means, said abutment means being adapted to positively stop further rotation of said switch assembly at a predetermined vacuum and to allow further rotation of said switch assembly at vacuums a predetermined amount greater than said predetermined vacuum.

3. An internal combustion engine ignition distributor of the type in which spark advance is dependent upon engine operating vacuum, said distributor comprising a housing, a shaft rotatably mounted through one end of said housing, a switch assembly, a cam follower operatively connected to said switch assembly, a cam member normally rotatable with said shaft and adapted to contact said cam follower in order to intermittently open and close said switch assembly for effecting a make and break of the ignition circuit, pressure responsive means operatively connected to said housing for causing a second relative motion between said cam member and said cam follower in addition to a first relative motion created by the rotation of said shaft, and means for positively stopping the maximum degree of said second relative motion at a predetermined vacuum and for allowing greater degrees of said second relative motion than said maximum at vacuums a predetermined amount greater than said predetermined vacuum.

4. An internal combustion engine ignition distributor of the type in which spark advance is dependent upon engine operating vacuum, said distributor comprising a housing, a shaft ro-tatably mounted through one end of said housing, a switch assembly, a cam follower operatively connected to said switch assembly, a cam member normally rotatable with said shaft and adapted to contact said cam follower in order to intermittently open and close said switch assembly for effecting a make and break of the ignition circuit, pressure responsive means operatively connected to said housing for causing a second relative motion between said cam member and said cam follower in addition to a first relative motion created by the rotation of said shaft, and means for positively stopping the maximum degree of said second relative motion at a predetermined vacuum and for allowing greater degrees of said second relative motion than said maximum at vacuums a predetermined amount greater than said predetermined vacuum, said means comprising an abutment, resilient means urging said abutment against said pressure responsive means in a direction resulting in a lesser second relative motion, and adjustment means cooperating with said resilient means for determining the initial force of said resilient means.

5. An internal combustion engine ignition distributor of the type in which spark advance is dependent upon engine operating vacuum, said distributor comprising a ,circuit interrupter, a member for operating said interrupter, a plate carrying thereon said interrupter, fluid pressure responsive means connected to said interrupter for rotating said interrupter about said member, and means for positively stopping further movement of said fluid pressure responsive means at a predetermined vacuum and allowing further movements of said fluid pressure responsive means greater than said maximum at vacuums a predetermined amount greater than said predetermined vacuum.

6. An internal combustion engine ignition distributor of the type in which spark advance is dependent upon engine operating vacuum, said distributor comprising a circuit interrupter, a member for operating said interrupter, an adjustable plate carrying thereon said interrupter, pivot means for adjusting said plate and interrupter with respect to said member, fluid pressure responsive means connected to said plate for rotating said plate and interrupter about said member, and abutment means positioned in the path of travel of said fluid pressure responsive means for stopping further movement of said fluid pressure responsive means at a predetermined vacuum and allowing further movements of said fluid pressure responsive means greater than said maximum at vacuums a predetermined amount greater than said predetermined vacuum.

7. An ignition distributor comprising a housing, a shaft rotatably mounted in said housing, a switch assembly, a cam member normally rotatable with said shaft and adapted to intermittently open and close said switch assembly for effecting a make and break of the ignition circuit, a breaker plate normally supporting said switch assembly and being mounted so as to be adjustable with respectto said housing, pressure responsive means operatively connected to said breaker plate for adjusting the same upon changes in pressure to which said means is subjected, and abutment means positioned in the path of travel of said pressure responsive means, said abutment means being constructed and arranged so as to positively stop the maximum adjustment of said breaker plate by said pressure responsive means in response to a predetermined pressure and to allow adjustments of said breaker plate greater than said maximum in response to pressures at a predetermined amount below said predetermined pressure.

8. An ignition distributor comprising a housing, a shaft rotatably mounted in said housing, a switch assembly, a cam member normally rotatable with said shaft and adapted to intermittently open and close said switch assembly for efiecting a make and break of the ignition circuit, and means for changing the relative position between said cam member and said switch assembly so as to advance said making and breaking of said ignition circuit in accordance with pressures to which said means is subjected, said means comprising a pressure responsive device having associated therewith spring-biased abutment means, said spring-biased abutment means being calibrated so as to positively stop the movement of said pressure responsive means in response to a predetermined pressure and to permit further movement of said pressure responsive means at pressures a predetermined amount lower than said predetermined pressure.

9. An internal combustion engine ignition distributor of the type in which ignition advance is in part dependent upon vacuums incident to the operation of the engine, said distributor comprising a housing, a shaft rotatably mounted in said housing, a switch assembly, a cam member normally rotatable with said shaft and adapted to intermittently open and close said switch assembly for etiectinga make and break of the ignition circuit, a breaker plate normally supporting said switch assembly and being adapted for relative motion with respect to said housing, vacuum responsive means operatively connected to said housing for moving said breaker plate, and abutment means positioned in the path of travel of said vacuum responsive means, said abutment means being adapted to positively stop the maximum movement of said breaker plate in response to a predetermined vacuum and to allow movements of said breaker plate greater than said maximum in response to vacuums a predetermined amount in excess of said predetermined vacuum.

10. In an ignition distributor of the type having vacuum responsive means for changing the angular relation between the distributor cam and its point of engagement with the movable ignition contact arm, means for positively stopping the movement of said vacuum responsive means in response to a predetermined vacuum and means to permit greater movement of said vacuum responsive means in response to vacuum a predetermined amount higher than said predetermined vacuum, said latter two means comprising a spring-biased abutment positioned in the path of travel of said pressure responsive means, the calibration of said spring-biased abutment determining the value of said predetermined vacuum.

11. In an ignition distributor of the type having vacuum responsive means for changing the relation between the distributor cam and its point of engagement with the movable ignition contact arm, means for positively stopping the movement of said vacuum responsive means in response to a predetermined vacuum and means to permit greater movement of said vacuum responsive means in response to vacuum a predetermined amount higher than said predetermined vacuum.

References Cited in the file of this patent UNITED STATES PATENTS 2,085,817 Melcher et a1 July 6, 1937 2,503,645 Westcott et a1 Apr. 11, 1950 2,508,851 Young et al May 23, 1950 2,640,116 Dyer et a1. May 26, 1953 2,731,523 Downing Jan. 17, 1956 FOREIGN PATENTS 514,670 Great Britain Nov. 15, 1939 

